Shares and bonds in Mr. Batista's flagship oil company, OGX Petroleo e Gas Participacoes, have slumped as the firm has fallen short of production targets. Most recently, OGX said it may have to halt work on its only producing field next year. Its woes have triggered a crisis of confidence across Mr. Batista's EBX group of heavy-industry firms.

About 200 bond creditors are expected to participate in an investor conference call on Thursday afternoon organized by U.S. law firm Cleary Gottlieb Steen & Hamilton, FTI Consulting and Brazilian law firm Pinheiro Neto Advogados, according to a person familiar with the situation.

The call will focus mainly on the $3.6 billion in bonds sold by OGX, as well as the $500 million in bonds sold by naval construction firm OSX Brasil, the person said. OGX's bonds, due 2018 and 2022, are trading around 20 cents on the dollar; OSX's bonds, which are backed by oil platforms under construction, are trading around 86 cents on the dollar.

The creditors will discuss the likelihood that Mr. Batista will make good on a commitment to invest a further $1 billion in OGX, as he's promised to do, the person said.

The chances the billionaire will inject extra cash into the oil firm via a put option seem to have dimmed after the two remaining independent members on the company's board stepped down Wednesday. Only independent members of the board can ask Mr. Batista to honor his commitment to invest more in the company, under the terms of the put option contract.

OGX investors are also questioning a $449 million payment to OSX for cancelling contracts to build oil platforms, the person said.

Meanwhile, a minority shareholder in OGX, Marcio de Melo Lobo, asked a Rio de Janeiro court to freeze Mr. Batista's assets, although he hasn't provided details of his case. Mr. Lobo, who owns roughly $17,620 of OGX shares, said in a telephone call he was expecting the Rio judge to rule on the request later Thursday. He said he would only provide more details after the judge's decision.

Sergio Bermudes, a lawyer for Mr. Batista, said Mr. Lobo's case has no legal basis because in Brazil assets can only be frozen in specific types of cases, such as when responsibility has been proven and there's a risk of assets being hidden.

Investors also want an investigation into comments that Mr. Batista made over the years regarding his companies. They say he exaggerated claims about the potential of the companies in his group.

Brazil's market regulator, the CVM, said at the beginning of this month that it would investigate OGX and other companies in the group, but didn't provide any details.

The watchdog so far has been studying press reports about the companies controlled by Mr. Batista and has asked the firms for clarifications of those reports, according to a person familiar with the situation. The CVM is also looking into the facts involving the put option extended by Mr. Batista to OGX, the person said without providing further details.